Check several features together.
Blue alone is not enough to identify it, because several flags in the picture have blue backgrounds. Also look for the gold colour, the individual stars and their circular arrangement. It is the combination that clearly identifies the correct image.
The circle stands for unity; the stars are associated with togetherness, solidarity and harmony. They do not form a map or a list of individual member countries. You therefore do not need to translate the current membership count into stars to recognise the flag.
The other three answers
The other three images differ in their basic visible shapes.
1
Image 1 has red and white stripes with a blue field containing white stars. It is not a gold circle of stars on an entirely blue field.
3
Image 3 shows a white world motif surrounded by branches on light blue. Neither the colour nor the shape of the central symbol matches the gold circle of stars.
4
Image 4 shows a white compass star with lines on dark blue. One white star differs from twelve separate gold stars in a circle.
Twelve stars do not mean twelve current member countries.
At the time reviewed, the EU has 27 member countries and its flag still has twelve stars. The star count is not adjusted when countries join or leave. Explaining the flag through membership numbers confuses a lasting symbol with a changing total.
The Council of Europe used the flag from 1955. The European Communities adopted it later, in 1985. The Council of Europe and the EU are different organisations; sharing a symbol does not make them the same institution.
The European flag · European Union ↗Blue background, twelve gold stars, one circle: the European flag.
Recognise the pattern; do not read a country count into the picture. The image number applies only to the arrangement shown.
Three words for this question
- der Sternenkreiscircle of stars
- Several stars arranged in a ring.
- das Sinnbildsymbol
- A visible sign representing an idea.
- die Solidaritätsolidarity
- Mutual support and standing together.